SCHOTT solutions no. 1/2012 > Concentrated Solar Power

Generation of concentrated solar power as shown here at one of the Andasol solar power plants located on the plateau of Granada is already showing significant macroeconomic effects in the model country of Spain. Photo: SCHOTT/J. Meyer

The New Value of Electricity

Electricity from solar thermal power plants offers an important advantage: it can be stored easily and then be fed in to meet the current demand. Therefore, many countries are interested in using this technology to establish a stable grid.

Thilo Horvatitsch

The long chains of meter-high parabolic mirrors from the Andasol solar power plants extend across the plateau of the province of Granada in southern Spain. With a capacity of 50 megawatts (MW) each, they are capable of supplying a half a million people with solar power. And they send out a signal on a promising future technology. After all, the generation of concentrated solar power (CSP) in the flagship country of Spain is already having significant macroeconomic effects. Studies show that the industry that includes both existing power plants and those under construction contributed more than 24,000 jobs and 1.6 billion euros to Spain’s gross domestic product in 2010 alone.

More and more countries are hoping to benefit from the many advantages that the CSP technology first commercialized in the 1980s offers. The CSP projects that have been realized in the United States, North and South Africa, the Middle East, Southeast Asia, India and China can attest to this. Besides being able to provide a local power supply in these countries, exporting power to places like Europe in the future is yet another goal.

Photo: SCHOTT/J. Meyer

And yet it is the rapid decline in the prices of its “sister technology” photovoltaics and wind power that is forcing CSP technology to communicate its strategic importance more actively in the public eye. At first sight, it seems that solar power will not be able to compete with the current costs of producing other types of renewable energy for some time to come. But according to a survey conducted by the industry association ESTELA, if one takes the projected capacity increases and technological advances – depending on the location, size and dispatchability of the power plants and the technology used – into consideration, there is still a great deal of potential to lower these costs. The rates could be lowered by up to 50 or 75 percent between 2015 and 2020 – with prices as low as 10 euro cents per kilowatt hour.

The greatest asset CSP technology has to offer, however, is the fact that the electricity it generates is dispatchable. This enables CSP plants to take advantage of their strengths in restructuring the energy mix to include renewable energy already today. CSP plants use concentrated sunlight to generate thermal energy. This can be stored rather easily in the form of liquid salt, for instance, before conventional steam turbines convert it into electricity. In other words, power can be retrieved and fed into the grid exactly when it is needed – for grid operators a significant advantage in terms of planning security. CSP technology offers ideal prospects in situations where the demand-oriented supply of electricity is extremely important for the stable ­operation of the grid.

As this graphic shows, the industry association ESTELA estimates the global potential for energy from CSP power plants to reach 1,100 gigawatts (GW) by 2050. 17.7 GW are now in operation, under construction or being funded. Source: ESTELA / Adaptation: dw

SCHOTT Solar has already delivered more than 800,000 receivers for projects all over the world. If these were placed end to end, they would cover the impressive distance of over 3,200 km. Photo: SCHOTT/J. Meyer

A contribution to grid stability

The fact that the output of CSP plants can be predicted extremely accurately represents yet another advantage: “CSP plants are being built in regions that have very constant levels of sunlight. This radiation is measured over a longer period before the plant is built, therefore it is fairly clear how much electricity will be produced at specific times of the year,” says Christoph Fark, Managing Director of SCHOTT Solar CSP . He also notes that this system is more sluggish than photovoltaics due to the intermediate step of “heat generation.” With photo­voltaics, bands of clouds immediately reduce the level of power production rather noticeably. “CSP power is particularly important because solar thermal power plants are the guarantors of grid stability. They not only spare us from having to build expensive conventional backup power plants to compensate for power shortages, but also make it easier to make the necessary commitments to investors and grid operators that are essential to planning and completing these projects,” Fark adds.

The grid-stabilizing capabilities of CSP technology are playing an important role in regions with rapidly growing energy demands like India and China, for instance, or countries like Morocco that have a fairly manageable grid capacity. After all, on the one hand, the goal is to make large volumes of energy available in a short period of time and, on the other, to prevent the grid from collapsing due to excessive energy input. CSP technology is thus needed. Phase one of India’s “Jawaharlal Nehru National Solar Mission,” for instance, calls for seven CSP plants with a total of 500 MW of output to be built by 2013.

SCHOTT Solar has also shipped receivers to India – and for many other projects all over the world. Since 2006, the company has grown to become the market leader in the area of advanced absorber tubes and equipped large parabolic trough power plants in Spain and the United States, among other countries. “We see much greater potential for CSP technology, especially in Africa, Asia, the Middle East and South America. The success story is therefore only just beginning,” Christoph Fark says. SCHOTT Solar intends to contribute to it mainly through innovative developments that enhance the efficiency of CSP power plant technology (see p. 17). The market is very receptive to these developments: the company will be shipping its one millionth receiver in the fall of 2012. <|

A parabolic trough power plant uses large mirrors to focus the solar radiation onto an absorber tube inside which a liquid is heated up. The heat generated is then converted into electricity by a steam turbine. The question of how much solar radiation a receiver can absorb and how much heat it emits is crucial to the efficiency of plants like these.

The advanced receiver from SCHOTT Solar features a new absorber coating that enables 95.5 percent to be used in the heat generation process. At the same time, the emission level of heat radiation is reduced to less than 9.5 percent. Further measures taken in the area of technology and design also increase the receiver’s ability to absorb more solar radiation.

To keep heat loss low even after many years of operation, SCHOTT Solar has also developed noble gas capsules that can be integrated into the receiver. These can be opened by using a laser at any time during the lifetime of the power plant. This also increases the longevity of the receivers – an important factor in the economic success of a CSP plant. <|